0:00:06 > 0:00:08We're about to embark on something
0:00:08 > 0:00:10most of us have never witnessed before.
0:00:12 > 0:00:15It will take us inside two of the most extraordinary
0:00:15 > 0:00:17structures in the natural world.
0:00:18 > 0:00:20Our feet and hands.
0:00:22 > 0:00:25Two parts of our body that make us who we are.
0:00:28 > 0:00:31I'm George McGavin, and as a biologist, I think that
0:00:31 > 0:00:36to truly understand our feet and hands, we need to look inside them.
0:00:38 > 0:00:42To do this, we've created our own dissection lab.
0:00:42 > 0:00:45We've brought together the tools, the technology
0:00:45 > 0:00:48and leading experts in human anatomy.
0:00:50 > 0:00:54Over two programmes, we're going to dissect a human foot and hand,
0:00:54 > 0:00:57to discover what makes them unique.
0:00:59 > 0:01:02And this time, we're looking at feet.
0:01:02 > 0:01:05We're going to reveal them as you've never seen them before.
0:01:07 > 0:01:10We'll take the foot apart systematically...
0:01:10 > 0:01:14We have to take the plantar fascia here and pull it back.
0:01:14 > 0:01:17..to uncover the incredible natural engineering
0:01:17 > 0:01:22that carries our weight and drives every step we take.
0:01:22 > 0:01:26That is the first time I've seen...inside the foot.
0:01:29 > 0:01:32Beyond the lab, I'll look at other animals whose feet give us
0:01:32 > 0:01:35clues to the origins of our own.
0:01:35 > 0:01:39So, my right foot is slightly more orang-like than my left foot?
0:01:39 > 0:01:41- Absolutely, yeah.- That's fantastic.
0:01:41 > 0:01:44And I want to discover exactly how our feet give us
0:01:44 > 0:01:50something that's rare in the animal kingdom, yet vital to our lives -
0:01:50 > 0:01:53the ability to balance on two feet.
0:01:53 > 0:01:54Oh, Jesus!
0:01:54 > 0:01:57I do...I don't want to move my legs.
0:01:59 > 0:02:01Taking a foot apart will be challenging,
0:02:01 > 0:02:03and it might provoke a strong reaction.
0:02:03 > 0:02:06But it will reveal how this extraordinary
0:02:06 > 0:02:09part of our anatomy has allowed us to stand
0:02:09 > 0:02:14and walk upright - fundamental abilities that define us as human.
0:02:28 > 0:02:32Of all life on our planet, no other animal has feet like ours.
0:02:32 > 0:02:35They allow us to walk on two legs -
0:02:35 > 0:02:39possibly the most significant step in our evolution.
0:02:40 > 0:02:43Our feet made us mobile and freed up our hands
0:02:43 > 0:02:48to use tools - skills that allowed us to dominate the planet.
0:02:52 > 0:02:55Our feet bear the weight of our body
0:02:55 > 0:02:58and propel our every step and stride -
0:02:58 > 0:03:01all the while performing a perpetual
0:03:01 > 0:03:05act of balance that keeps us upright.
0:03:05 > 0:03:07Yet we rarely think about them.
0:03:09 > 0:03:13What we consider to be our greatest physical achievements
0:03:13 > 0:03:15depend on our feet.
0:03:15 > 0:03:18How fast we run, how high we jump, our agility,
0:03:18 > 0:03:23our balance, all depend on the remarkable capabilities of the foot.
0:03:25 > 0:03:28To discover how our foot makes all this possible,
0:03:28 > 0:03:30we've set up our dissection lab
0:03:30 > 0:03:34in the Anatomy Museum of Glasgow University.
0:03:38 > 0:03:41And to perform the delicate operation of dissecting
0:03:41 > 0:03:45a real human foot, we've brought together an expert team.
0:03:48 > 0:03:53Dr Kartik Hariharan is one of the country's leading foot surgeons.
0:03:55 > 0:04:00Feet have always fascinated me. They're unique organs.
0:04:00 > 0:04:01They're very complex.
0:04:01 > 0:04:05And if you look at it, we place very conflicting demands on feet.
0:04:05 > 0:04:09We want them to be soft and supple and mobile,
0:04:09 > 0:04:11whilst on the other hand, we want them to be rigid and strong,
0:04:11 > 0:04:14so that we can push off and propel ourselves.
0:04:14 > 0:04:17And it's only because of the finesse of the foot,
0:04:17 > 0:04:20its technical complexity, that it is able to offer
0:04:20 > 0:04:23both of these functions to you, without too much effort.
0:04:23 > 0:04:25Well, I think it's about time
0:04:25 > 0:04:27- we actually saw how it all worked. - Absolutely.
0:04:31 > 0:04:36Anatomy expert Dr Quentin Fogg is going to lead our dissecting team.
0:04:39 > 0:04:41He has carefully prepared our specimen,
0:04:41 > 0:04:43following the strict medical
0:04:43 > 0:04:47and ethical protocols that govern the dissection of human tissue.
0:04:51 > 0:04:54- Hi, Quentin.- Hi, George. - So, this is the foot
0:04:54 > 0:04:58- that we're going to dissect?- Yes. This is the foot and the lower limb
0:04:58 > 0:05:00of a person who donated themselves
0:05:00 > 0:05:02for anatomical research and education.
0:05:02 > 0:05:04Now, to some people this might seem
0:05:04 > 0:05:08quite a shocking thing, almost bad taste.
0:05:08 > 0:05:09But how would you answer that?
0:05:09 > 0:05:12It's quite a commonplace thing in your world, isn't it?
0:05:12 > 0:05:16It is, and it's a real opportunity for us to explore
0:05:16 > 0:05:19the body in a way that you don't really get in any other format.
0:05:19 > 0:05:22You can look at the internet, you can look at amazing drawings
0:05:22 > 0:05:25and wonderful photos in books, and you don't really get an
0:05:25 > 0:05:28understanding of how it works to the same level as we're going to get.
0:05:30 > 0:05:31Our team is ready,
0:05:31 > 0:05:34and the moment has come to make the first incision.
0:05:35 > 0:05:38It's something few people ever get to see.
0:05:38 > 0:05:42I'm fascinated, but also a little apprehensive.
0:05:42 > 0:05:45We're going to start off by looking at the sole of the foot,
0:05:45 > 0:05:47by cutting the skin here and removing this,
0:05:47 > 0:05:50to see the layers directly underneath that.
0:05:50 > 0:05:52So I'm going to get started.
0:05:56 > 0:05:58And then just going down the side of the foot...
0:06:06 > 0:06:09Now, that skin at the heel is pretty tough, isn't it?
0:06:09 > 0:06:11Yeah. It's many layers thick,
0:06:11 > 0:06:15and a lot of these layers are actually dead skin cells.
0:06:15 > 0:06:19The body heaps it all up simply to thicken it up,
0:06:19 > 0:06:22so that can act as a shock-absorbing pad.
0:06:25 > 0:06:28Ooh, now, the skin's coming right off the heel.
0:06:28 > 0:06:33I have to confess, I'm...I'm feeling slightly queasy about this,
0:06:33 > 0:06:38and nu...not in a severe way, but it's quite a disturbing view.
0:06:39 > 0:06:43That is the first time I've seen...inside the foot.
0:06:43 > 0:06:45There's a huge amount of fat there -
0:06:45 > 0:06:47just masses of it!
0:06:47 > 0:06:53That's fat that's packaged in a very special form to maximise
0:06:53 > 0:06:56the shock-absorbing capabilities of the heel.
0:06:58 > 0:06:59How is it arranged, though?
0:06:59 > 0:07:01Because it looks almost, erm,
0:07:01 > 0:07:04- like a, you know, a sponge. Is that fair to say?- Yeah, well,
0:07:04 > 0:07:07Well, it is anything but a sponge, because its strength is phenomenal.
0:07:07 > 0:07:12It's almost like a hydraulic pad, where you've got these fat
0:07:12 > 0:07:17packets arranged in little discrete sections, with little fibrous walls.
0:07:17 > 0:07:20So, they work in a fashion,
0:07:20 > 0:07:24so that your weight is distributed quite evenly.
0:07:24 > 0:07:27So it's not one big lump - it's not like a cushion.
0:07:27 > 0:07:30- It's more like bubble wrap... - OK, yeah.
0:07:30 > 0:07:32..where you've got multiple sections
0:07:32 > 0:07:34of fat, so it's able to dissipate
0:07:34 > 0:07:38shock and forces that go through it in a much more efficient fashion.
0:07:41 > 0:07:44So, in this first stage of our dissection, we've already seen
0:07:44 > 0:07:47two vital parts of the foot.
0:07:48 > 0:07:51The tough outer skin, and a thick layer of fat beneath,
0:07:51 > 0:07:54that combine to act as a shock-absorber.
0:07:57 > 0:08:00But our skin has another important function.
0:08:00 > 0:08:02To see what that is, there's no way around it -
0:08:02 > 0:08:05I'm going to have to bare my own feet.
0:08:05 > 0:08:07I'll make an exception! Ha-ha!
0:08:09 > 0:08:11- Right, there you go.- OK.
0:08:11 > 0:08:13Now Hari can get his hands on my bare feet,
0:08:13 > 0:08:17he can show another crucial role that the skin performs.
0:08:17 > 0:08:20A very important function is that of sensitivity -
0:08:20 > 0:08:23the ability to perceive touch.
0:08:23 > 0:08:26And a very simple example is tickling.
0:08:26 > 0:08:28- Yeah!- Ha-ha-ha!
0:08:28 > 0:08:30- He-he(!)- So, you can see how,
0:08:30 > 0:08:33as soon as I put my fingers to your...
0:08:33 > 0:08:36to the soles of your feet, you try and retract them away.
0:08:36 > 0:08:40So, that is a very important protective mechanism,
0:08:40 > 0:08:43so that you don't step on something sharp without recognising it.
0:08:43 > 0:08:46Now, it's not just sensation which is
0:08:46 > 0:08:49flat and equal across the whole of the foot.
0:08:49 > 0:08:51Different parts have different sensations,
0:08:51 > 0:08:53and let me try and illustrate that to you.
0:08:55 > 0:08:58OK, what I want you to do is, I want you to close your eyes,
0:08:58 > 0:09:00so that you can't see what I'm doing.
0:09:00 > 0:09:03I want you to tell me how many points you can feel, OK?
0:09:06 > 0:09:08- How many points can you feel on that?- One.
0:09:08 > 0:09:10And there?
0:09:10 > 0:09:11One.
0:09:11 > 0:09:14- And there?- One.
0:09:14 > 0:09:16- There?- One.
0:09:20 > 0:09:21One?
0:09:23 > 0:09:25Two.
0:09:25 > 0:09:27That's a beautiful illustration of how
0:09:27 > 0:09:30the acuteness of sensation changes.
0:09:30 > 0:09:33So at the back, in the region of the heel,
0:09:33 > 0:09:36where the skin is very thick, it's important to feel pressure.
0:09:36 > 0:09:39But as you come towards the toes, your toes will have to do more.
0:09:39 > 0:09:42They'll have to be able to feel the shape of things,
0:09:42 > 0:09:46the sharpness of things, and so, as I got towards the toes, you were able
0:09:46 > 0:09:49to perceive that I was touching you with two points as opposed to one.
0:09:49 > 0:09:50Elegant!
0:10:03 > 0:10:06So, the soles of our feet have two important functions -
0:10:06 > 0:10:10to sense the ground below them and support the weight above them.
0:10:12 > 0:10:16But what actually happens when we walk and run?
0:10:16 > 0:10:19How do our feet perform these movements
0:10:19 > 0:10:21that are so fundamental to our lives?
0:10:21 > 0:10:24STARTING PISTOL FIRES
0:10:28 > 0:10:34To understand this, we need to take a closer look at our feet in action.
0:10:34 > 0:10:37So I've come to Dundee to meet Professor Rami Abboud.
0:10:37 > 0:10:42He's an expert in biomechanics - the science of how our body moves.
0:10:42 > 0:10:45And he's been researching exactly what our feet are doing
0:10:45 > 0:10:48when we walk and run.
0:10:48 > 0:10:51We can run a series of tests to show you what happens with the foot
0:10:51 > 0:10:53and leg when we walk and run.
0:10:53 > 0:10:56Rami is investigating how much pressure
0:10:56 > 0:10:59the weight of our body puts on our feet.
0:11:00 > 0:11:03So he has assembled an arsenal of technology - cameras,
0:11:03 > 0:11:06pressure pads, movement sensors,
0:11:06 > 0:11:10all set up to analyse what happens with each footstep.
0:11:12 > 0:11:15First, Rami wants to show me what happens when we walk.
0:11:16 > 0:11:20As you can see, she hits the ground at the heel, moves forward to the
0:11:20 > 0:11:24forefoot, comes off the ground, and this is the normal way we walk.
0:11:24 > 0:11:26We all walk in this fashion.
0:11:26 > 0:11:29This is the data from the pressure pad.
0:11:29 > 0:11:32Red areas show where the pressure on the foot is highest.
0:11:32 > 0:11:36We can see this happen when the heel hits the floor.
0:11:36 > 0:11:39In fact, up to twice the volunteer's weight
0:11:39 > 0:11:41goes through her heel as she lands.
0:11:43 > 0:11:45It's why the tough skin and the pad of fat we saw
0:11:45 > 0:11:50in our dissection are so important - they help absorb this shock.
0:11:51 > 0:11:53And as the rest of the foot comes down,
0:11:53 > 0:11:55we can see how the pressure shifts.
0:11:57 > 0:12:00You can notice here that most of the pressure that we saw under
0:12:00 > 0:12:02the heel is now localised under the ball of the foot -
0:12:02 > 0:12:05and we're ready to push forward.
0:12:05 > 0:12:09And the last point of contact will come with the toes,
0:12:09 > 0:12:11and mainly the big toe.
0:12:11 > 0:12:16So that's a complete movement, from heel strike to leaving the ground.
0:12:16 > 0:12:18Absolutely.
0:12:20 > 0:12:22We take thousands of steps every day,
0:12:22 > 0:12:27and each one puts the pressure of twice our body weight on our feet.
0:12:30 > 0:12:33Next, Rami's going to show me what's different when we run.
0:12:39 > 0:12:43As you can see now from the pressure patterns on the screen,
0:12:43 > 0:12:49there is an impact of the forces from heel to toes again,
0:12:49 > 0:12:53and the striking point here is that the pressure that you see under the
0:12:53 > 0:12:57heel, which is reaching sometimes up to three times your body weight...
0:12:57 > 0:13:00- So that's very high. - That's extremely high.
0:13:00 > 0:13:03And the heel will have to try to absorb that.
0:13:03 > 0:13:05So, landing on our heel when we run
0:13:05 > 0:13:10sends a force three times our body weight up our leg.
0:13:11 > 0:13:13And Rami's computer shows us
0:13:13 > 0:13:16the direction that the force of the impact travels in.
0:13:16 > 0:13:20You can see this massive force that is going through
0:13:20 > 0:13:24the system from the ankle all the way to the hip.
0:13:24 > 0:13:27The arrow shows that the force from the heel strike is going right
0:13:27 > 0:13:32through all the major joints in the leg - the ankle, knee and hip.
0:13:32 > 0:13:36And this puts enormous pressure on these vital joints.
0:13:37 > 0:13:40What's really obvious is, if you compare this to walking,
0:13:40 > 0:13:44there's a point where both feet are clearly off the ground.
0:13:44 > 0:13:46- As you see here.- But every time
0:13:46 > 0:13:48the heel comes down and you've got the full body weight
0:13:48 > 0:13:51- plus times three, banging away at your joints.- Absolutely.
0:13:51 > 0:13:55This is a repetitive movement that you do during running,
0:13:55 > 0:13:57so it's not happening once or twice.
0:13:59 > 0:14:02Every year, it's estimated that
0:14:02 > 0:14:05up to 75% of regular runners suffer an injury.
0:14:07 > 0:14:09Some research suggests that the impact
0:14:09 > 0:14:13generated by heel-striking could be a contributing factor.
0:14:16 > 0:14:20And Rami's research has revealed something surprising.
0:14:20 > 0:14:23It seems the pressure caused by the heel strike could be
0:14:23 > 0:14:28a relatively new problem that we humans have inflicted on ourselves.
0:14:29 > 0:14:32To see why, we're repeating the running experiment,
0:14:32 > 0:14:34but this time, with a difference.
0:14:36 > 0:14:38Now this is really interesting.
0:14:38 > 0:14:41We've asked Charlotte to run with no shoes on,
0:14:41 > 0:14:45and, that's remarkable, there is no heel impact at all.
0:14:45 > 0:14:48It's very normal. This is how most of us run.
0:14:48 > 0:14:52When we run bare feet, we never land on the heel like we do
0:14:52 > 0:14:55when we're walking, we will only run on the ball of the foot.
0:14:55 > 0:14:58If you actually try to tend to run heel-to-toe,
0:14:58 > 0:15:02you'll be in deep pain, and, if you look at the actual screen there,
0:15:02 > 0:15:06all the impact is being taken by the ball of the foot.
0:15:06 > 0:15:08You're landing instantly on the most stable position
0:15:08 > 0:15:10and structure of the foot.
0:15:10 > 0:15:14Landing on the ball of the foot instead of the heel completely
0:15:14 > 0:15:18changes the way the force of the impact passes through our body.
0:15:19 > 0:15:24As you can see, the actual force is not going through the ankle,
0:15:24 > 0:15:27it's actually in front of the ankle, pointed
0:15:27 > 0:15:31backwards behind the knee. This force is now absorbed by the calf muscles.
0:15:31 > 0:15:34It's not going through the joint.
0:15:34 > 0:15:37So, when the ball of the foot strikes the ground first,
0:15:37 > 0:15:42our calf muscles are able to take some of the strain off our joints.
0:15:42 > 0:15:44So your research is actually indicating that
0:15:44 > 0:15:48when we run with shoes on, we're actually running in the wrong way?
0:15:48 > 0:15:49Well, absolutely.
0:15:49 > 0:15:53As human beings, I think we are born to run, and that goes back
0:15:53 > 0:15:58to our ancestors when they used to chase game over long distances.
0:15:58 > 0:16:02And they've done that without shoes, or any cushioning material.
0:16:02 > 0:16:06Wearing shoes encourages you to land on your heel,
0:16:06 > 0:16:08and that might cause serious injury.
0:16:12 > 0:16:16Today, it's hard to imagine going about our lives without shoes on.
0:16:18 > 0:16:20But although they make our feet feel more comfortable,
0:16:20 > 0:16:24it seems wearing them might have an unwelcome consequence.
0:16:25 > 0:16:28So it looks like we're not using our feet in the way that
0:16:28 > 0:16:30evolution shaped them.
0:16:30 > 0:16:32Keeping them warm and protected in shoes
0:16:32 > 0:16:35has added to the strain we put on them.
0:16:39 > 0:16:44So, with every step we take, our feet cope with huge forces.
0:16:44 > 0:16:48But what is it inside the foot that makes this possible?
0:16:48 > 0:16:52That's what we're looking for in the next part of our dissection.
0:16:52 > 0:16:54Right, where have we got to?
0:16:55 > 0:16:58We've just removed the layer of fat, and then we've got
0:16:58 > 0:17:01a really important tissue hiding right underneath that.
0:17:01 > 0:17:04This is a special layer of tissue, just really like a bunch of strings,
0:17:04 > 0:17:07known as the plantar fascia, which is a really important
0:17:07 > 0:17:10layer for adding mechanical strength to the sole of the foot.
0:17:10 > 0:17:14So you've removed the whole of the sole of the foot, plus all that fat.
0:17:14 > 0:17:16Hari, what does that actually do?
0:17:16 > 0:17:20This is probably one of the most important structures, particularly
0:17:20 > 0:17:24in trying to understand the complex biomechanical workings of the foot.
0:17:24 > 0:17:30It connects the heel or the hindfoot to the toes which form the forefoot.
0:17:30 > 0:17:34So you've got three structures - the plantar fascia, the heel
0:17:34 > 0:17:38and the toes - forming this wonderful weight-bearing system.
0:17:40 > 0:17:43The bones of the foot form a familiar structure -
0:17:43 > 0:17:47an arch, particularly good for bearing weight.
0:17:47 > 0:17:51Its two pillars are the heel and the ball of the foot.
0:17:51 > 0:17:54But what's less familiar is the tissue that binds them -
0:17:54 > 0:17:56the plantar fascia.
0:17:56 > 0:17:57It's a part of the foot most of us
0:17:57 > 0:18:02know very little about - yet it's crucial to the way our feet work.
0:18:04 > 0:18:06So, you can see this very elegant structure,
0:18:06 > 0:18:09taking a point of attachment to the heel,
0:18:09 > 0:18:14and then moving forward, very thick to begin with, and bunched up,
0:18:14 > 0:18:18and then separating out into many strands like a fan.
0:18:18 > 0:18:21This works by tensioning and de-tensioning as you put weight
0:18:21 > 0:18:23and you take weight off.
0:18:23 > 0:18:25You can actually see this as I put
0:18:25 > 0:18:27the foot into a standing position.
0:18:27 > 0:18:28- You can see...- Ah, yeah.
0:18:28 > 0:18:30..the thing tenses, and as I relax it,
0:18:30 > 0:18:32it becomes a bit looser and floppier.
0:18:32 > 0:18:35So, that's a very unique function
0:18:35 > 0:18:38of this particular structure,
0:18:38 > 0:18:40and it works almost like a spring,
0:18:40 > 0:18:42- but a very, very taut and tight spring.- Wow.
0:18:46 > 0:18:48As Quentin continues the dissection,
0:18:48 > 0:18:52I want to learn more about how this spring-like mechanism works.
0:18:53 > 0:18:56To help me is Dr Niall Macfarlane,
0:18:56 > 0:18:59an expert in the biomechanics of the human body.
0:19:00 > 0:19:02So, Niall, can you explain to me
0:19:02 > 0:19:05some of the essential elements of the physics of the foot?
0:19:05 > 0:19:08Yeah, I've got a simple model here that might help.
0:19:08 > 0:19:10So, obviously, this part represents your toe.
0:19:11 > 0:19:13This is the ankle and this is the heel.
0:19:13 > 0:19:17So, the first thing that's important for our gait, for walking,
0:19:17 > 0:19:18is to lift our toe.
0:19:18 > 0:19:23That muscle action to lift the toe
0:19:23 > 0:19:27puts some stress onto the plantar fascia.
0:19:27 > 0:19:28I can actually feel that.
0:19:28 > 0:19:31As I lift my toe up, my arch is becoming, you know, stretched.
0:19:31 > 0:19:33- Yes, that's right.- Strained.
0:19:33 > 0:19:35And that is really important to the physics,
0:19:35 > 0:19:37the biomechanics, of the action of the foot.
0:19:37 > 0:19:39When we hit the ground and your heel strikes...
0:19:39 > 0:19:44So, when we hit the ground, your weight presses down your ankle.
0:19:44 > 0:19:48That puts much more energy into that plantar fascia.
0:19:48 > 0:19:51It acts like a spring - stores the energy -
0:19:51 > 0:19:55and when you lift your foot off the ground to take the next step,
0:19:55 > 0:19:56lo and behold,
0:19:56 > 0:19:57it springs you in the air
0:19:57 > 0:20:00and gives you some energy to take your step forward.
0:20:00 > 0:20:02It's essentially an energy store,
0:20:02 > 0:20:04- and it's what put's the spring in your step.- It does, yeah.
0:20:07 > 0:20:11So, the foot is an extremely efficient energy converter -
0:20:11 > 0:20:14storing energy that comes down through the ankle,
0:20:14 > 0:20:17then releasing it to help propel us forward.
0:20:17 > 0:20:20But where does power to drive this action come from?
0:20:24 > 0:20:26OK, so let's make this incision...
0:20:26 > 0:20:28To find what powers our foot, we
0:20:28 > 0:20:30need to look beyond the foot itself,
0:20:30 > 0:20:32beneath the skin of the lower leg.
0:20:34 > 0:20:37We're going to uncover something that's key to our movement -
0:20:37 > 0:20:39the calf muscles.
0:20:39 > 0:20:42When we open this up, we'll see different types of tissue.
0:20:42 > 0:20:46We'll see the yellow tissue that looks like little
0:20:46 > 0:20:48collections of sponges - more fat.
0:20:49 > 0:20:53How is the power produced in the calf transferred
0:20:53 > 0:20:54all the way to the foot?
0:20:54 > 0:20:58OK, this is a very good example of probably the biggest muscle
0:20:58 > 0:21:00that has its influence in the foot.
0:21:00 > 0:21:06This is the muscle in the calf, which then works on the bone.
0:21:06 > 0:21:10That is the end point of where this muscle works.
0:21:10 > 0:21:12And the conduit for the transfer of that
0:21:12 > 0:21:15energy into the heel would be the Achilles tendon.
0:21:16 > 0:21:19The Achilles tendon is something I've often heard about.
0:21:19 > 0:21:23But now I can actually see why it's so important to how we use our feet.
0:21:25 > 0:21:29It's bigger than I imagined - it emerges from the calf muscle
0:21:29 > 0:21:31and attaches it to the heel bone.
0:21:33 > 0:21:36So if we looked at the tendon
0:21:36 > 0:21:40slowly transforming from the muscular structures.
0:21:40 > 0:21:42So the muscle ends roughly about here,
0:21:42 > 0:21:47and slowly, you find this wonderful tubular structure.
0:21:48 > 0:21:50Let me show you how it actually works.
0:21:55 > 0:21:59So, at this point, I've let the foot dangle down,
0:21:59 > 0:22:03and I'm going to hold the calf muscle here,
0:22:03 > 0:22:04and I'm going to squeeze it.
0:22:04 > 0:22:07And you can immediately see how, by contracting
0:22:07 > 0:22:13and shortening this muscle, you can see the front of the foot
0:22:13 > 0:22:18move down, and conversely, the heel actually lifting up.
0:22:18 > 0:22:20So that's what happens when you go up on your toes.
0:22:20 > 0:22:22That's correct.
0:22:22 > 0:22:23If you look at this now, you can
0:22:23 > 0:22:26see the anatomic definition very, very nicely.
0:22:26 > 0:22:29You've got these two big bellies of muscle that are going down
0:22:29 > 0:22:31to attach onto the tendon.
0:22:31 > 0:22:35The tendon is very broad here - much narrower further down,
0:22:35 > 0:22:38but much thicker, much more concentrated fibres.
0:22:38 > 0:22:43You can now appreciate that this tendon is responsible
0:22:43 > 0:22:45for us walking, standing, jumping -
0:22:45 > 0:22:48- all of the things that we take for granted...- Mmm.
0:22:48 > 0:22:49..in our day-to-day lives.
0:22:53 > 0:22:57So, our leg muscles and our Achilles tendon are working together
0:22:57 > 0:22:59to provide the power we need for movement.
0:23:02 > 0:23:05And this propels our every step and stride,
0:23:05 > 0:23:08every jump and leap.
0:23:09 > 0:23:13It's what takes us to the pinnacle of our physical achievement.
0:23:18 > 0:23:21The deeper we delve into the workings of the foot, the more
0:23:21 > 0:23:24it becomes apparent that nature has come up with some incredibly
0:23:24 > 0:23:28complex engineering to support our weight and allow us to move around.
0:23:30 > 0:23:32We humans move in a way that's
0:23:32 > 0:23:35extremely rare in the animal kingdom -
0:23:35 > 0:23:39we have four limbs, yet we only use two of them to walk.
0:23:40 > 0:23:43So what is that makes our feet different?
0:23:44 > 0:23:48To answer that, I've come to the Natural History Museum at
0:23:48 > 0:23:52St Andrews University to look at the feet of other four-limbed animals.
0:23:54 > 0:23:55Now, in order to move around,
0:23:55 > 0:23:59all animals need feet that can perform two basic functions.
0:23:59 > 0:24:04They've got to achieve stability AND mobility at the same time.
0:24:04 > 0:24:08For some animals, you have to trade off one against the other.
0:24:12 > 0:24:17Take the elephant. An adult male can weigh a colossal seven tonnes.
0:24:19 > 0:24:23And just to support that enormous weight, their feet have evolved
0:24:23 > 0:24:25in particular ways - some of them surprising.
0:24:28 > 0:24:32Well, this is the hind foot of a young elephant, and you can see
0:24:32 > 0:24:36the bones are extremely strong and thick - this is the heel bone here.
0:24:36 > 0:24:38When the elephant moves around,
0:24:38 > 0:24:41its foot is actually in this position, and that's because
0:24:41 > 0:24:44this space here at the back
0:24:44 > 0:24:48is occupied by a massive pad of very specialised fat.
0:24:48 > 0:24:50The result of this is that elephants
0:24:50 > 0:24:53when they walk are actually walking on tiptoes.
0:24:53 > 0:24:56It's a bit like they're wearing high heels, but in this case, the
0:24:56 > 0:24:59high heel is formed by this enormous
0:24:59 > 0:25:02pad of specialised fat that helps to bear
0:25:02 > 0:25:07the enormous weight of the animal and spread it out over a large area.
0:25:07 > 0:25:10An elephant is definitely not built for speed.
0:25:10 > 0:25:12This is an example of animal
0:25:12 > 0:25:15that has had to trade off mobility for stability.
0:25:20 > 0:25:21But for other animals,
0:25:21 > 0:25:24the ability to run fast is a matter of life and death.
0:25:26 > 0:25:28Take the horse or the zebra.
0:25:28 > 0:25:32In the wild, these animals evolved for life on the plains.
0:25:32 > 0:25:35They needed to cover long distances and outrun their enemies.
0:25:35 > 0:25:39For them, mobility is the greater priority,
0:25:39 > 0:25:42and their feet look very different to the elephant's,
0:25:42 > 0:25:44as we can see when we look at their skeleton.
0:25:46 > 0:25:48This is the hip girdle or pelvis.
0:25:48 > 0:25:51Here's the femur, the thighbone of the leg.
0:25:51 > 0:25:54Kneecap. Here is the lower bone of the leg.
0:25:54 > 0:25:57But the really interesting stuff happens further down.
0:25:57 > 0:26:04A full one third of the length of a horse's leg is made up by its foot.
0:26:04 > 0:26:07This is the ankle joint here, here is the heel bone,
0:26:07 > 0:26:10and this is the long bone of the foot.
0:26:10 > 0:26:13And if I can compare this to my hand,
0:26:13 > 0:26:18we have of course five fingers and toes. In a horse, all that
0:26:18 > 0:26:23remains is the middle toe, that runs right the way back up here.
0:26:23 > 0:26:27In essence, horses are running on their middle toe.
0:26:29 > 0:26:33But running is just one way to cover great distances.
0:26:37 > 0:26:40Kangaroos and wallabies do it differently.
0:26:41 > 0:26:45And to achieve this, they have evolved very unusual feet.
0:26:48 > 0:26:51An animal like a wallaby gets around by hopping, and
0:26:51 > 0:26:55so not surprisingly, its hind legs make up about half of its height.
0:26:57 > 0:26:59The long bones of a wallaby's foot give it a great
0:26:59 > 0:27:01deal of leverage against the ground,
0:27:01 > 0:27:06and a second toe off the side here gives it a bit more stability.
0:27:08 > 0:27:11But stability can be achieved by other means,
0:27:11 > 0:27:14because not all four-limbed animals walk on the ground.
0:27:17 > 0:27:19A chameleon is a highly-specialised sort of animal.
0:27:19 > 0:27:21It doesn't need to be terribly fast.
0:27:21 > 0:27:26What it DOES need to do is hang on to branches very tightly indeed.
0:27:26 > 0:27:29And its foot is highly-specialised.
0:27:29 > 0:27:31It's called a zygodactyl foot.
0:27:31 > 0:27:35Two of its toes go in one direction and three go in the other,
0:27:35 > 0:27:38so they can wrap around the branch very tightly indeed.
0:27:42 > 0:27:45So, all these animals evolved their own solutions to the
0:27:45 > 0:27:48trade-off between stability and mobility.
0:27:48 > 0:27:52And this allows them to move around in their different environments.
0:27:53 > 0:27:55But although their feet appear very different,
0:27:55 > 0:27:58if you look carefully, you can see intriguing
0:27:58 > 0:28:02similarities between these diverse animals and us.
0:28:06 > 0:28:10If I take as an example the long bone of the middle toe,
0:28:10 > 0:28:14it varies a lot from species to species.
0:28:14 > 0:28:18Here it is in the wallaby, tiny and slender.
0:28:18 > 0:28:22Here it is in the horse, the major bone of the foot.
0:28:22 > 0:28:25In the elephant, it's here.
0:28:25 > 0:28:27And in the human, here.
0:28:29 > 0:28:31And the fact that all these animals have similar
0:28:31 > 0:28:34bones in their feet is no coincidence.
0:28:35 > 0:28:37When you look at the limbs of a tetrapod animal -
0:28:37 > 0:28:42that's a four-legged animal - you see a basic plan.
0:28:42 > 0:28:45There's an upper leg or arm bone,
0:28:45 > 0:28:49two lower leg or arm bones,
0:28:49 > 0:28:52then you get a collection of small bones
0:28:52 > 0:28:56in the wrist or in the foot.
0:28:56 > 0:29:01And then you've got five fingers or toes.
0:29:01 > 0:29:03And that's called the pentadactyl limb.
0:29:03 > 0:29:05Pentadactyl - five fingers.
0:29:05 > 0:29:10All four-limbed animals today are descended from an ancestor
0:29:10 > 0:29:15that lived over 340 million years ago that had a pentadactyl limb.
0:29:16 > 0:29:19It's an incredibly versatile basic plan,
0:29:19 > 0:29:23that nature has modified in a myriad of ways to allow animals to
0:29:23 > 0:29:26stand and move around their environments.
0:29:26 > 0:29:28And one of those adaptations
0:29:28 > 0:29:33is our own foot, which has evolved in its own unique way.
0:29:34 > 0:29:38The pentadactyl limb structure truly is a marvel of nature.
0:29:38 > 0:29:42It's a blueprint that evolution has adapted in countless ways to
0:29:42 > 0:29:44allow different animals to survive
0:29:44 > 0:29:48and move around in all the variety of habitats on Earth.
0:29:48 > 0:29:50To me as a biologist,
0:29:50 > 0:29:56it's an illustration of evolution at its most elegant and awe-inspiring.
0:29:59 > 0:30:03So, our hands and our feet are based on this pentadactyl structure.
0:30:05 > 0:30:08And although most of us assume they have very different functions,
0:30:08 > 0:30:12we can in fact use them in surprisingly similar ways.
0:30:13 > 0:30:17Tom Yendell was born without arms, but that hasn't stopped him
0:30:17 > 0:30:18from becoming an artist.
0:30:20 > 0:30:23That is absolutely extraordinary.
0:30:23 > 0:30:26I mean, I couldn't do that with my hands.
0:30:26 > 0:30:30It's 51 years of practice.
0:30:30 > 0:30:33When did you draw your first picture?
0:30:33 > 0:30:36I think when I was about, er...
0:30:36 > 0:30:37Well, I don't know.
0:30:37 > 0:30:39I've always used it, so -
0:30:39 > 0:30:41- when did you draw YOUR first picture? - I can't remember.
0:30:41 > 0:30:44- Probably about five, I suppose. - Yeah.
0:30:44 > 0:30:46When I was five, I had artificial arms,
0:30:46 > 0:30:51and the doctors put socks and shoes on me, so I couldn't use my feet.
0:30:51 > 0:30:54And I've got some film of me scribbling with this hook,
0:30:54 > 0:30:58and being very frustrated, because I knew I could do it much quicker
0:30:58 > 0:31:00and much easier with my feet.
0:31:00 > 0:31:03And you use your feet for everything?
0:31:03 > 0:31:04Everything. Yeah.
0:31:04 > 0:31:07I mean, everything you do with your hands, I do with my feet.
0:31:08 > 0:31:12Tom trained his feet to do the everyday tasks that we
0:31:12 > 0:31:15take for granted - but he also uses them for painting.
0:31:17 > 0:31:22And you're now a very well-respected artist around the world.
0:31:22 > 0:31:24Well, I'm an artist!
0:31:24 > 0:31:27- And you've got some images here. - Yeah.
0:31:27 > 0:31:31Yeah, I've got some pictures that you can have a look at.
0:31:35 > 0:31:36This is what I'm...
0:31:36 > 0:31:41What I'm known for really is very "graphicy" flowers.
0:31:41 > 0:31:44And I paint for the Mouth and Foot Painting Artists.
0:31:44 > 0:31:48We're a group of 800 artists around the world that all
0:31:48 > 0:31:50earn their living through painting.
0:31:52 > 0:31:55Seeing Tom's work, I'm intrigued by his ability,
0:31:55 > 0:31:58- and I'm keen to see how much - I- can do with my own feet
0:31:59 > 0:32:02So, I think we'll just, just write our names, really.
0:32:04 > 0:32:06There you are. Tom Yendell.
0:32:06 > 0:32:08Right. Right, OK.
0:32:09 > 0:32:12HE HUMS TO HIMSELF IN CONCENTRATION
0:32:15 > 0:32:16'As I struggle with the pen,
0:32:16 > 0:32:20'I'm struck by how remarkable Tom's ability is.
0:32:21 > 0:32:23'MY feet just can't seem to manage the precision
0:32:23 > 0:32:26'and control that HE makes look so easy.'
0:32:28 > 0:32:30Me O's gone funny.
0:32:32 > 0:32:34Right.
0:32:34 > 0:32:36- Give me the pen.- Oh, sorry.
0:32:36 > 0:32:39I'll show the audience how it should be spelt.
0:32:39 > 0:32:40GEORGE LAUGHS
0:32:40 > 0:32:44- What is it, G-E-O-R-G-E, is that right?- Yeah.
0:32:44 > 0:32:46- There you go.- Brilliant.
0:32:47 > 0:32:49Must try harder, eh?
0:32:49 > 0:32:51- Must try harder. Practise.- Yeah.
0:32:51 > 0:32:54Use your feet, because they are so useful.
0:32:54 > 0:32:56- Take your shoes off when you're at home.- Yes.
0:32:56 > 0:32:59- I think I will, actually. - Yeah. Be a shoeless environment,
0:32:59 > 0:33:04and you'll be amazed at how quickly you can start doing things.
0:33:04 > 0:33:06Can I have that as a souvenir?
0:33:06 > 0:33:08You can.
0:33:08 > 0:33:12I should get you making a paper aeroplane really, shouldn't I?
0:33:12 > 0:33:14Oh, come on, Tom! Come on!
0:33:14 > 0:33:16Thank you very much.
0:33:18 > 0:33:22Through constant practice, Tom can use his feet to do things
0:33:22 > 0:33:25that most of us could only achieve with our hands.
0:33:25 > 0:33:30But what is it inside his foot that allows him to do this?
0:33:30 > 0:33:33That's what Quentin's looking for next.
0:33:33 > 0:33:37We're about to unveil all of the intrinsic muscles of the foot,
0:33:37 > 0:33:40all the small muscles inside here that control
0:33:40 > 0:33:41the toes in different ways.
0:33:41 > 0:33:44To see them, we have to take the plantar fascia here,
0:33:44 > 0:33:45and pull it back.
0:33:45 > 0:33:48And one of the first things we'll notice is the small muscles
0:33:48 > 0:33:51underneath here, the lots of little tiny tendons.
0:33:51 > 0:33:54And are these ones that we're actually are able to
0:33:54 > 0:33:56shift our toes individually with?
0:33:56 > 0:33:58- Yeah, these... - ..and wiggle them about?
0:33:58 > 0:34:00These are the wiggling muscles. Indeed!
0:34:00 > 0:34:04Now, the degree to which individuals are able to wiggle their toe,
0:34:04 > 0:34:06that varies quite a bit.
0:34:06 > 0:34:10Yes, I think it all depends upon the flexibility of the individual
0:34:10 > 0:34:13per se, and how well-developed these muscles are.
0:34:15 > 0:34:18So, it's likely that the intrinsic muscles in Tom's feet
0:34:18 > 0:34:21are more developed than in most of us.
0:34:21 > 0:34:25And this allows him to use his feet with such precision and control.
0:34:26 > 0:34:29So, if we look inside the foot here, we can see these small muscles.
0:34:29 > 0:34:32And if we lift that up, we see there are these really thin,
0:34:32 > 0:34:35slender tendons running down to each individual toe,
0:34:35 > 0:34:38apart from the big toe. And if I pull on them as a group...
0:34:39 > 0:34:42..the tendons will pull on each toe, and make them move.
0:34:43 > 0:34:45If I pull on one at a time,
0:34:45 > 0:34:49we don't really get a single movement from just the one toe.
0:34:49 > 0:34:51The one next to it will still be working.
0:34:51 > 0:34:54If you looked at it in evolutionary terms,
0:34:54 > 0:34:56in the time when feet were
0:34:56 > 0:34:57used as climbing organs
0:34:57 > 0:35:01and grasping organs, these muscles would have been very well developed.
0:35:01 > 0:35:05But, of course, the anatomy of the foot would have been different then.
0:35:05 > 0:35:07The big toe would have been more like a thumb.
0:35:07 > 0:35:10And you would have power and pincer grip, in order to be able to
0:35:10 > 0:35:12do the finer movements that's
0:35:12 > 0:35:14demanded more of a hand than a foot.
0:35:22 > 0:35:26The small, intrinsic muscles in our foot are a remnant from a time
0:35:26 > 0:35:29when our ancestors lived in the trees.
0:35:29 > 0:35:30And just like primates today,
0:35:30 > 0:35:32they used their feet
0:35:32 > 0:35:34more like we use our hands -
0:35:34 > 0:35:36for holding and grasping.
0:35:37 > 0:35:40So what else can the feet of our close cousins tell us
0:35:40 > 0:35:43about how our own feet have evolved?
0:35:44 > 0:35:48I've come to Chester Zoo to look at the feet of the orang-utan.
0:35:48 > 0:35:51Orang-utans are primarily tree dwellers,
0:35:51 > 0:35:53just like our early ancestors.
0:35:53 > 0:35:56So to find out more about how we came to have the feet
0:35:56 > 0:36:00we have today, I want to compare the orangs' feet with our own.
0:36:06 > 0:36:09Professor Robin Crompton is a world expert on understanding
0:36:09 > 0:36:12how our ancestors walked.
0:36:12 > 0:36:15Key to his research is studying modern primates.
0:36:17 > 0:36:20How do orang-utans use their feet?
0:36:20 > 0:36:22Very much as we'd use our hands.
0:36:22 > 0:36:27They have, first of all, a big toe which is like our thumb,
0:36:27 > 0:36:31and held at quite an angle to the other fingers.
0:36:31 > 0:36:35So they can actually wrap their thumb around a narrow branch,
0:36:35 > 0:36:39- a vine, just as we can do with our hands.- Mmm.
0:36:39 > 0:36:45Equally, the rest of the foot can curl around even very narrow
0:36:45 > 0:36:48supports like vines and small branches,
0:36:48 > 0:36:50to meet and grasp round in a powerful grasp like that.
0:36:53 > 0:36:55High-speed cameras capture
0:36:55 > 0:36:57the movement of the orang's feet.
0:36:57 > 0:37:01They clearly show a distinctive bending motion -
0:37:01 > 0:37:05this allows their feet to curl and grip in ways that our foot can't.
0:37:07 > 0:37:10This flexibility seems so alien to us,
0:37:10 > 0:37:12because our feet appear to be far more rigid.
0:37:12 > 0:37:17In fact, for a long time, we thought that having a rigid foot was
0:37:17 > 0:37:19a defining feature of humanity -
0:37:19 > 0:37:23something that separated us from our primate cousins.
0:37:23 > 0:37:26But it seems the story is not so clear-cut.
0:37:30 > 0:37:33Robin's been comparing the differences in primate
0:37:33 > 0:37:36and human feet when they walk.
0:37:36 > 0:37:38To do this, he uses pressure pads.
0:37:39 > 0:37:43As the orang-utan walks across, we can see it has an awkward gait,
0:37:43 > 0:37:45walking on the side of its foot.
0:37:46 > 0:37:49So, this is the classic orang-utan pattern.
0:37:50 > 0:37:54We're seeing very little contact under the heel,
0:37:54 > 0:37:57a large peak in front of the heel
0:37:57 > 0:37:59in the middle part of the foot...
0:37:59 > 0:38:03'The red areas show where most pressure is exerted on the pad.
0:38:03 > 0:38:06'And Robin is particularly interested
0:38:06 > 0:38:08'in this small pressure peak here.'
0:38:10 > 0:38:15What's causing this peak is a small joint in the orang's foot.
0:38:15 > 0:38:17It's called the mid-tarsal joint.
0:38:17 > 0:38:21It's very mobile, and this is what allows the orang's foot to be
0:38:21 > 0:38:25so flexible - perfectly adapted for life in the trees.
0:38:27 > 0:38:30The human foot also has a mid-tarsal joint,
0:38:30 > 0:38:33but it was long believed we'd lost the ability to flex
0:38:33 > 0:38:37at this joint - we thought it was locked and rigid.
0:38:37 > 0:38:39But Robin isn't so sure.
0:38:39 > 0:38:41He's been investigating
0:38:41 > 0:38:45whether OUR mid-tarsal joint can still flex today.
0:38:45 > 0:38:48So, can he find any evidence of it in my footprint?
0:38:48 > 0:38:50There's no sign of it in my left foot,
0:38:50 > 0:38:52but in my right foot, there's a surprise.
0:38:52 > 0:38:57So, George, this is the still data from your footprint record.
0:38:57 > 0:39:01You can see that you produced a mid-tarsal pressure peak.
0:39:01 > 0:39:04- This is my foot here? This is my right foot.- Right there, yep.
0:39:04 > 0:39:09You can see it appearing just there, right in between the heel
0:39:09 > 0:39:13- and the ball of the foot - in the middle there!- Oh, yeah, there it is!
0:39:13 > 0:39:17This is something that humans are just not supposed to have.
0:39:17 > 0:39:20- So my right foot is slightly more orang-like?- Absolutely, yes.
0:39:20 > 0:39:24That's fantastic. That's really, really interesting!
0:39:26 > 0:39:29Over the last few years, Robin has been gathering pressure pad
0:39:29 > 0:39:32data from large groups of people.
0:39:32 > 0:39:36His results challenge what we thought we knew about our feet.
0:39:36 > 0:39:39They suggest that far from being locked and rigid,
0:39:39 > 0:39:43our mid-tarsal joint can bend when we walk, just like the orang's.
0:39:44 > 0:39:47Well, it's quite definitely shown that the human foot is just
0:39:47 > 0:39:49nothing like as stiff as we thought it was.
0:39:49 > 0:39:53In fact, in our data set, two-thirds of people
0:39:53 > 0:39:58produce a substantial mid-foot pressure peak, on both feet,
0:39:58 > 0:40:00within five minutes of walking.
0:40:01 > 0:40:06Robin's work has shown our feet are not just rigid platforms.
0:40:06 > 0:40:10In most of us, the middle of our foot still has a flexible
0:40:10 > 0:40:13joint that we've inherited from our ancestors.
0:40:15 > 0:40:18So if it isn't our skeleton that makes our foot rigid after all,
0:40:18 > 0:40:20what is it?
0:40:22 > 0:40:25What's very clear now is that it's primarily the soft tissues -
0:40:25 > 0:40:28that is, the ligaments, the muscles and the tendons.
0:40:28 > 0:40:34And what they're giving our feet is particularly an adjustable stiffness.
0:40:34 > 0:40:38And that's very important, as it turns out, because it's made
0:40:38 > 0:40:42a big difference in our ability to adjust to life on the ground.
0:40:42 > 0:40:45And the fact that humans retained a foot that essentially
0:40:45 > 0:40:48can be flexible when it needs to be, I think almost certainly is
0:40:48 > 0:40:52one of the major factors which has made humans so successful
0:40:52 > 0:40:55when we started to move out of forest, into open country.
0:40:58 > 0:41:02So, it turns out that our feet can be both flexible AND rigid -
0:41:02 > 0:41:04and that's what makes them so special.
0:41:07 > 0:41:11It was this unique combination that enabled us to adjust
0:41:11 > 0:41:14to different terrains, and allowed us to spread across the planet.
0:41:17 > 0:41:20One of the crucial factors that gives our feet this exceptional
0:41:20 > 0:41:24versatility is the soft tissues that bind our bones together.
0:41:28 > 0:41:30And back at our dissection,
0:41:30 > 0:41:33Quentin has uncovered some of these.
0:41:34 > 0:41:36One of the key structures
0:41:36 > 0:41:37in here are ligaments.
0:41:37 > 0:41:38And ligaments really
0:41:38 > 0:41:40just strap bone to bone.
0:41:40 > 0:41:42Their job is to define the range
0:41:42 > 0:41:44of movement of the joint.
0:41:44 > 0:41:45So, when two bones are next
0:41:45 > 0:41:47to each other, they need to be able
0:41:47 > 0:41:48to move a little bit - but not
0:41:48 > 0:41:50too much, or they fall apart.
0:41:50 > 0:41:51- Right.- So a ligament is
0:41:51 > 0:41:52the strap that holds them together.
0:41:52 > 0:41:54And in this view of the foot,
0:41:54 > 0:41:56we've got lots of little bones here,
0:41:56 > 0:41:59and we can see the joints between them.
0:41:59 > 0:42:03And then there is one great example from the outside of your ankle
0:42:03 > 0:42:07of a big ligament strapping from this bone to the next.
0:42:07 > 0:42:10So the really important thing about these,
0:42:10 > 0:42:13other than defining the range of motion of these joints,
0:42:13 > 0:42:16is that they can help stabilise each of these joints,
0:42:16 > 0:42:19make sure they're just in the right position,
0:42:19 > 0:42:21and it never costs them any energy.
0:42:21 > 0:42:24So we have other things that help us stabilise,
0:42:24 > 0:42:26like muscles and tendons,
0:42:26 > 0:42:28but to make a muscle contract,
0:42:28 > 0:42:30we need to spend some energy.
0:42:30 > 0:42:32And therefore it tires.
0:42:32 > 0:42:34It gets tired reasonably quickly.
0:42:34 > 0:42:36One of the things that makes us
0:42:36 > 0:42:39a very successful upright walking animal
0:42:39 > 0:42:41is that we can go for fairly long periods of time
0:42:41 > 0:42:43with those muscles working,
0:42:43 > 0:42:44but eventually it's going to tire.
0:42:44 > 0:42:48When it tires or they're unavailable or we get surprised,
0:42:48 > 0:42:52then these ligaments are the things that hold the bones together.
0:42:52 > 0:42:54We know they're not perfect,
0:42:54 > 0:42:56because when our foot gets into a really weird position,
0:42:56 > 0:42:58these can be the things that break,
0:42:58 > 0:43:01- when you sprain an ankle, for example.- Exactly, yeah.
0:43:01 > 0:43:04If you go over on your ankle, that's what you tear.
0:43:04 > 0:43:08Sometimes. You can have more superficial injuries,
0:43:08 > 0:43:09or less serious ones,
0:43:09 > 0:43:13but the really, really severe ones are when these things break.
0:43:13 > 0:43:16That's not a good situation for these joints.
0:43:17 > 0:43:19'Our ligaments are vital to holding
0:43:19 > 0:43:22'the architecture of our foot together.
0:43:22 > 0:43:26'And as Quentin works towards the end of our dissection,
0:43:26 > 0:43:28'I'm going to see how our feet perform
0:43:28 > 0:43:29'when we push them to the extreme.'
0:43:33 > 0:43:36PIANO MUSIC
0:43:37 > 0:43:40Eve Mutso is a soloist with Scottish Ballet.
0:43:46 > 0:43:50- It is quite incredible.- Thank you!
0:43:50 > 0:43:55- When did you start? - I started when I was ten.- Ten.
0:43:55 > 0:43:58Before that, I did gymnastics, which helped,
0:43:58 > 0:44:02I think, to develop the suppleness of the foot.
0:44:02 > 0:44:04But with the ballet, I started when I was ten.
0:44:10 > 0:44:13Every part of the foot we've seen in our dissection
0:44:13 > 0:44:15is working to its very limits.
0:44:16 > 0:44:19Together, they are an amazing natural machine,
0:44:19 > 0:44:20tuned to perfection.
0:44:22 > 0:44:25If you looked at the power behind the calf,
0:44:25 > 0:44:28you can see how it's pulling her heels up
0:44:28 > 0:44:31in such an extreme and remarkable fashion
0:44:31 > 0:44:33so that she's able to go onto the one toe.
0:44:33 > 0:44:38You can see the definition of the muscle at the back of the calf there.
0:44:38 > 0:44:40At the same time, you can see how the ankle
0:44:40 > 0:44:42has been bent forward in, again,
0:44:42 > 0:44:45an almost superhuman fashion.
0:44:45 > 0:44:47All that force has to go right down
0:44:47 > 0:44:49through the foot bones,
0:44:49 > 0:44:52right through the toes, in a straight line, virtually.
0:44:52 > 0:44:54The foot bones are now strung
0:44:54 > 0:44:56together by the powerful ligaments,
0:44:56 > 0:44:58the smaller muscles of the foot,
0:44:58 > 0:45:01into this incredible arched structure,
0:45:01 > 0:45:02which is bearing the weight
0:45:02 > 0:45:06and transferring it to the floor through a very small surface area.
0:45:06 > 0:45:08She's virtually standing on her toes
0:45:08 > 0:45:09at the moment, as you can see.
0:45:09 > 0:45:11To make it even more complex,
0:45:11 > 0:45:14she is now able to twirl around doing her pirouette,
0:45:14 > 0:45:17which, again, for me, represents something so remarkable
0:45:17 > 0:45:20from a biomechanical perspective.
0:45:20 > 0:45:23Is Eve's foot inherently stronger than mine?
0:45:23 > 0:45:26Is it more flexible, obviously more flexible, than mine?
0:45:26 > 0:45:28But I mean, surely, there's a compromise,
0:45:28 > 0:45:32a trade-off between being flexible and being strong.
0:45:32 > 0:45:34Well, that is the remarkable trade-off
0:45:34 > 0:45:36that Eve's managed to achieve.
0:45:36 > 0:45:39That can only come by years and years of training
0:45:39 > 0:45:41and getting the muscle to do what you want it to do,
0:45:41 > 0:45:45getting the joints moving in such an unnatural position,
0:45:45 > 0:45:50yet being able to hold that in a rigid and sturdy fashion.
0:45:50 > 0:45:53This remarkable natural engineering allows Eve to achieve
0:45:53 > 0:45:56extraordinary things with her feet,
0:45:56 > 0:45:57but it comes at a price.
0:45:59 > 0:46:00I've had several operations,
0:46:00 > 0:46:03but I guess you just have to deal with those.
0:46:03 > 0:46:04And also...
0:46:05 > 0:46:09Yeah, I think just coming back from injuries,
0:46:09 > 0:46:11it's when you realise that you love your profession
0:46:11 > 0:46:13and you work around them.
0:46:13 > 0:46:15Well, Eve, thank you very much.
0:46:15 > 0:46:18I feel like a completely clumsy elephant in comparison.
0:46:21 > 0:46:23The ballerina en pointe is, to my mind,
0:46:23 > 0:46:27the pinnacle of what the human foot can achieve.
0:46:27 > 0:46:30The entire weight of a human body
0:46:30 > 0:46:34balanced on one small part of the foot - the big toe.
0:46:35 > 0:46:38This is the final key structure within the foot
0:46:38 > 0:46:40we haven't yet examined,
0:46:40 > 0:46:43and the dissecting team are ready to reveal it.
0:46:45 > 0:46:48So, George, we are now at the grand finale
0:46:48 > 0:46:51in a sequence of wondrous events.
0:46:51 > 0:46:54The big toe - the big boy of the front of the foot,
0:46:54 > 0:46:57a truly remarkable structure for a variety of reasons.
0:46:57 > 0:46:59The amount of force that goes
0:46:59 > 0:47:01through that part of the foot
0:47:01 > 0:47:03is absolutely enormous.
0:47:03 > 0:47:07If you can picture that for any movement of the body to occur,
0:47:07 > 0:47:11the final thrust must come off at the big toe level.
0:47:11 > 0:47:13So your heel hits the ground first,
0:47:13 > 0:47:15your foot is landing flat,
0:47:15 > 0:47:17and then all of the weight
0:47:17 > 0:47:18is transferred onto the front of the foot
0:47:18 > 0:47:22and most of this weight is carried by the big toe.
0:47:25 > 0:47:28So running down the length of the foot here is the big tendon
0:47:28 > 0:47:32that goes and powers this really important big toe.
0:47:32 > 0:47:36What's really impressive, and makes this a perfect driver of the body,
0:47:36 > 0:47:39is that if we follow the tendon all the way back up,
0:47:39 > 0:47:41it runs through the entire length of the foot.
0:47:41 > 0:47:43It goes underneath your ankle
0:47:43 > 0:47:46and then all the way up into the back of your leg
0:47:46 > 0:47:50and when this guy contracts, it's always in the perfect position
0:47:50 > 0:47:54to pull this tendon and power the body forward through the big toe.
0:47:54 > 0:47:55It's the only muscle at the back here
0:47:55 > 0:47:58which is perfectly aligned with the big toe,
0:47:58 > 0:48:00no matter what position your foot is in.
0:48:00 > 0:48:03And you can transfer your entire body weight
0:48:03 > 0:48:05right down your leg, right down your foot
0:48:05 > 0:48:06and out the end of your big toe.
0:48:06 > 0:48:08And it's all taken on that.
0:48:08 > 0:48:09Well, it is actually the end
0:48:09 > 0:48:13of a long chain of energy-efficient mechanisms,
0:48:13 > 0:48:16mechanisms that store and transfer energy,
0:48:16 > 0:48:19mechanisms that convert that energy into activity,
0:48:19 > 0:48:23so that you are able to walk in a smooth and efficient manner,
0:48:23 > 0:48:27you are able to run in a smooth and efficient manner.
0:48:27 > 0:48:29I can see that you really love the big toe.
0:48:29 > 0:48:34I love the big toe because it is the final sequence in a box of tricks
0:48:34 > 0:48:37that nature has provided for us in our feet.
0:48:40 > 0:48:44Our dissection has revealed the intricate structures
0:48:44 > 0:48:45within the human foot.
0:48:47 > 0:48:49We've seen how the muscles and tendons,
0:48:49 > 0:48:52ligaments and bones all combine to form
0:48:52 > 0:48:54an incredibly sophisticated machine
0:48:54 > 0:48:57that allows us to stand and walk.
0:49:01 > 0:49:04But this ability is about more than just mechanics.
0:49:04 > 0:49:07There's one final role that our feet play.
0:49:10 > 0:49:14It's a process that starts from our earliest years.
0:49:14 > 0:49:17We can't walk from birth - we need to learn how to do it.
0:49:22 > 0:49:25Most of us take the ability to walk upright for granted,
0:49:25 > 0:49:28but when you think about it, it is quite incredible -
0:49:28 > 0:49:31all our weight balancing on two small points.
0:49:31 > 0:49:35So how do we perform that balancing act on a day-to-day basis?
0:49:37 > 0:49:40Here at Manchester Metropolitan University,
0:49:40 > 0:49:44a group of scientists are trying to answer that question.
0:49:44 > 0:49:46- Your lab, this is it. - Yes, this is the lab.
0:49:46 > 0:49:48- It's like an aircraft hangar. - Well, yes.
0:49:48 > 0:49:51Professor Ian Loram studies how we control movement,
0:49:51 > 0:49:55and he's something of an expert on balance.
0:49:55 > 0:49:58So, Ian, what are the factors that are involved
0:49:58 > 0:50:00in us actually standing upright?
0:50:00 > 0:50:03OK, well, you've got vision, which really tells you
0:50:03 > 0:50:06the orientation of all the buildings and those vertical lines around you.
0:50:06 > 0:50:08You've got your vestibular apparatus,
0:50:08 > 0:50:11which is really that thing in your inner ear,
0:50:11 > 0:50:14which tells you how your head is orientated
0:50:14 > 0:50:17or whether it's accelerating and rotating.
0:50:17 > 0:50:19And then you have this thing called proprioception.
0:50:19 > 0:50:22Now, that's the sense whereby I can shut my eyes
0:50:22 > 0:50:26and touch my nose, or even harder, touch my fingers together,
0:50:26 > 0:50:27without actually seeing them.
0:50:27 > 0:50:30Absolutely, so, even with your eyes closed,
0:50:30 > 0:50:32that just gives you that sense
0:50:32 > 0:50:36of where all the parts of your body are in relation to each other.
0:50:39 > 0:50:42Proprioception is a vital sense.
0:50:42 > 0:50:43How it works is that our muscles
0:50:43 > 0:50:47are constantly sending electrical signals to our brain
0:50:47 > 0:50:49telling it their precise position.
0:50:50 > 0:50:53This stream of information helps our brain understand
0:50:53 > 0:50:55which way is up and down,
0:50:55 > 0:50:59and where all the parts of our body are in relation to each other.
0:51:02 > 0:51:07To investigate just how important proprioception is to our balance,
0:51:07 > 0:51:09Ian has designed an experiment.
0:51:09 > 0:51:11And he's about to try it out on me.
0:51:13 > 0:51:17Well, this is the first time I've ever shaved my legs.
0:51:18 > 0:51:22All I have to do in the experiment is stand up.
0:51:22 > 0:51:25OK, George, I'm now going to blindfold you.
0:51:25 > 0:51:28Even with a blindfold on, it's simple,
0:51:28 > 0:51:30because with every tiny movement they make,
0:51:30 > 0:51:35my muscles are constantly sending signals to my brain.
0:51:35 > 0:51:38And my brain uses this information to tell me
0:51:38 > 0:51:41where my body is in relation to the ground.
0:51:41 > 0:51:44Well, I mean, that's fine, I can walk around.
0:51:44 > 0:51:46I can stay upright. It's fairly easy.
0:51:48 > 0:51:50I'm relying on my proprioception,
0:51:50 > 0:51:53but Ian has found a way to stop it working.
0:51:54 > 0:51:58OK, George, what we're now going to do is test your balance.
0:51:58 > 0:52:01We're going to ask you to control the motion of the board
0:52:01 > 0:52:02with your muscles,
0:52:02 > 0:52:05which will make the board go forwards and backwards.
0:52:05 > 0:52:06Three, two, one...
0:52:08 > 0:52:11Now I'm standing on a moveable board.
0:52:11 > 0:52:14My feet have no connection with solid ground.
0:52:14 > 0:52:17Every time they move, the board moves too,
0:52:17 > 0:52:20and the signals they send to my brain are confusing.
0:52:22 > 0:52:26Oh, I-I couldn't control that at all.
0:52:26 > 0:52:29Because my muscles aren't moving in relation to a fixed point,
0:52:29 > 0:52:34my brain can't build up an accurate picture of the world around me.
0:52:34 > 0:52:38That's impossible. I'm really unsure which way is up.
0:52:40 > 0:52:43I'm amazed by how disorientated I feel
0:52:43 > 0:52:45without the ground beneath my feet.
0:52:46 > 0:52:48And it shows me my feet are playing a role
0:52:48 > 0:52:51that I was never conscious of before.
0:52:52 > 0:52:56When you're on the ground, your ankles are rotating,
0:52:56 > 0:53:00and that signals the stretching information to the brain,
0:53:00 > 0:53:03and your brain uses that information
0:53:03 > 0:53:06to control the muscles and keep you in balance.
0:53:06 > 0:53:08So when I was on the shelf that moved with the machine,
0:53:08 > 0:53:12my ankles were effectively locked? I wasn't getting any information?
0:53:12 > 0:53:14Absolutely, so, really,
0:53:14 > 0:53:17you were deprived of that sensory information.
0:53:22 > 0:53:25So what allows us to balance is a crucial interaction
0:53:25 > 0:53:29between our foot and leg muscles and our brain.
0:53:29 > 0:53:31Some muscles provide the brain with information,
0:53:31 > 0:53:36and the brain then tells particular muscles to tense or relax.
0:53:36 > 0:53:40But there are occasions when this communication breaks down,
0:53:40 > 0:53:43and the results can be dramatic.
0:53:43 > 0:53:45Right, Ian, what now?
0:53:45 > 0:53:47Ian illustrates this with a second experiment
0:53:47 > 0:53:51that's as deceptively easy as the first -
0:53:51 > 0:53:53walk across a plank about six inches wide.
0:53:55 > 0:53:58But Ian then reveals the hard part.
0:54:00 > 0:54:01Oh!
0:54:07 > 0:54:08Ah!
0:54:14 > 0:54:17I know this is just as easy
0:54:17 > 0:54:19as it was on the floor,
0:54:19 > 0:54:20but I'm now...
0:54:23 > 0:54:26I don't want to move my legs.
0:54:26 > 0:54:27Oh!
0:54:29 > 0:54:30Whoa...
0:54:32 > 0:54:34I'm... Oh, Jesus!
0:54:39 > 0:54:40Oh!
0:54:40 > 0:54:42Most of us have had this feeling -
0:54:42 > 0:54:44something that is simple in one situation
0:54:44 > 0:54:47suddenly becomes incredibly difficult.
0:54:50 > 0:54:53Ian, why did I find that so hard?
0:54:53 > 0:54:57- Yeah, you obviously were afraid. - Yes.- That's a very sane response.
0:54:57 > 0:54:59But the thing is, your muscles were tensing up,
0:54:59 > 0:55:02and that was distorting the proprioceptive information
0:55:02 > 0:55:05coming back into your brain, and that was affecting your balance.
0:55:05 > 0:55:09So, of course, that made you tense up even more.
0:55:09 > 0:55:12So you have this possibility of a vicious cycle developing.
0:55:14 > 0:55:16This vicious cycle helps explain
0:55:16 > 0:55:19why my balance was so poor on the plank.
0:55:20 > 0:55:23Fear of falling made my muscles tense
0:55:23 > 0:55:25and this interfered with the crucial information
0:55:25 > 0:55:27they were providing to my brain.
0:55:29 > 0:55:33A psychological fear has produced a very real physical response.
0:55:34 > 0:55:36I'm frozen again.
0:55:37 > 0:55:41So this proprioceptive sense is really important.
0:55:41 > 0:55:46Yeah, proprioception is measuring these minute changes all the time
0:55:46 > 0:55:48and feeding that information into the brain.
0:55:48 > 0:55:51The brain uses that information to contract the muscles
0:55:51 > 0:55:54and that interaction is maintaining balance.
0:55:54 > 0:55:57And it's what makes us able to actually stand upright.
0:55:57 > 0:56:00Yes, and I still find it so amazing that, standing still,
0:56:00 > 0:56:04all this is going on all the time and we barely realise it.
0:56:07 > 0:56:10So even standing still, the muscles in our foot and calf
0:56:10 > 0:56:13are making constant minute changes
0:56:13 > 0:56:15just to keep us upright.
0:56:15 > 0:56:18And as they do this, those muscles provide our brain
0:56:18 > 0:56:22with essential information to help us balance.
0:56:22 > 0:56:24Our feet really are remarkable.
0:56:24 > 0:56:27They're sensitive enough to gather information
0:56:27 > 0:56:28about the world around us
0:56:28 > 0:56:33and yet strong enough to bear all that weight pressing down on them.
0:56:33 > 0:56:36Yet we're hardly even aware of the complex interactions
0:56:36 > 0:56:39that go on between our feet and our brain
0:56:39 > 0:56:43that allow us to perform the everyday act of walking.
0:56:51 > 0:56:54Most of us take thousands of steps every day.
0:56:56 > 0:56:59And every step is possible only thanks
0:56:59 > 0:57:03to the elegant and intricate mechanisms within our feet.
0:57:03 > 0:57:06I've been astonished by the complex interplay
0:57:06 > 0:57:08between all the different parts of the foot
0:57:08 > 0:57:12coming together that allow us to walk, run and jump.
0:57:16 > 0:57:18Our dissections of a human hand and foot
0:57:18 > 0:57:21have revealed the natural engineering
0:57:21 > 0:57:24that allows us to perform tasks we take for granted.
0:57:26 > 0:57:29Dissecting a hand, I saw the intricate machinery
0:57:29 > 0:57:33that gives us a unique combination of power and precision.
0:57:37 > 0:57:40And in our foot dissection, I've seen the complex mechanisms
0:57:40 > 0:57:43that allow our feet to be so adaptable -
0:57:43 > 0:57:48the outer layers that combine protection and sensitivity,
0:57:48 > 0:57:51muscles that provide balance and power...
0:57:52 > 0:57:56..ligaments that allow our feet to be both flexible and rigid...
0:57:59 > 0:58:03..and I've seen the ingenious structures that recycle energy
0:58:03 > 0:58:06with every single step we take.
0:58:06 > 0:58:07Dissecting hands and feet,
0:58:07 > 0:58:12I've certainly gained a new respect for the extremities of my limbs
0:58:12 > 0:58:16and they've caused me to think again about what it is to be human.